1. Field of the Invention
This invention relates to polymeric toothed endless power transmission belts and to an improved method and apparatus for making same.
2. Prior Art Statement
Toothed endless power transmission belts made primarily of polymeric material are well known in the art and two commonly used types of such belts are so-called cog-type belts and synchronous belts. In cog-type belts teeth are provided in each belt for the main purposes of improved belt flexibility and controlled transverse rigidity. In synchronous belts each belt has alternating teeth and grooves which mesh with cooperating grooves and teeth respectively of cooperating toothed pulleys for the purpose of transmitting rotational forces.
However, regardless of the type of toothed endless power transmission belt, it is important that the teeth formed for endless belts (and particularly those made primarily of rubber) be formed with precision yet in an economical manner.
It has been proposed in U.S. Pat. No. 3,999,914 to provide a continuous reinforced toothed strip made of elastomeric or synthetic material such as polyurethane or polyamide or similar extruding material and such toothed strip is made by injecting the material into an arc-shaped mold defined by a rotating toothed wheel converted by a steel band.
It has also been proposed in U.S. Pat. No. 4,083,838 to wind a prefabricated continuous reinforced toothed strip made of polyurethane, polyamide, and the like, and of the type disclosed in U.S. Pat. No. 3,999,914 employing a special apparatus and method to define a so-called reinforced tube by heating and fusing adjoining portions of the toothed strip being wound and utilizing such tube for the purpose of cutting endless toothed belts therefrom.
It has also been disclosed in U.S. Pat. No. 4,123,946 to extrude a plain strip of polymeric material having load-carrying means extending throughout the length of the strip, wind such strip in a helical pattern on a drum, and cure the wound strip to form a belt sleeve which is without teeth and has smooth right circular cylindrical inside and outside surfaces. The belt sleeve is then cut to define endless belts. The plain strip of polymeric material may be rubber or a thermoplastic material and the polymeric material may have fibers embedded therein in a random manner.
It has also been proposed in U.S. patent application Ser. No. 034,698, filed Apr. 30, 1970 to make a long synchronous belt by forming a first toothed belt sleeve on a toothed cylinder, cutting the first belt sleeve in a helical pattern to define a toothed strip of extended length, winding the toothed strip on toothed cylinder means to form a second toothed belt sleeve, and then cutting the second sleeve to define toothed endless belts.